/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2017-2025 Payara Foundation and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://github.com/payara/Payara/blob/main/LICENSE.txt
 * See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at legal/OPEN-SOURCE-LICENSE.txt.
 *
 * GPL Classpath Exception:
 * The Payara Foundation designates this particular file as subject to the "Classpath"
 * exception as provided by the Payara Foundation in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
 *
 * Contributor(s):
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */

package fish.payara.microprofile.jwtauth.eesecurity;

import java.time.Duration;
import java.util.Optional;
import java.util.function.Supplier;

public class KeyLoadingCache {

    private final Supplier<CacheableString> keySupplier;
    private Duration ttl;
    private Duration retainOnErrorDuration;
    private long lastUpdated;
    private long lastError;
    private Optional<String> key;


    public KeyLoadingCache(Supplier<CacheableString> keySupplier) {
        this.ttl = Duration.ZERO;
        this.keySupplier = keySupplier;
    }

    public Optional<String> get() {
        long now = System.currentTimeMillis();
        if (now - lastUpdated > ttl.toMillis()) {
            refresh();
        }

        return key;
    }

    private synchronized void refresh() {
        long now = System.currentTimeMillis();
        if (now - lastUpdated > ttl.toMillis()) {
            try {
                CacheableString result = keySupplier.get();
                key = result.getValue();
                ttl = result.getCacheTTL();
                retainOnErrorDuration = result.getRetainOnErrorDuration();
                lastUpdated = now;
                lastError = 0L;
            } catch (Exception exception) {
                if (lastError == 0L) {
                    lastError = now;
                }
                if (key != null && key.isPresent() && retainOnErrorDuration != null && !retainOnErrorDuration.isZero()) {
                    long elapsedSinceLastError = now - lastError;
                    if (elapsedSinceLastError < retainOnErrorDuration.toMillis()) {
                        // No exception is thrown so get() will return the key.
                        return;
                    }
                    throw new RuntimeException("An error occurred while fetching the key and the retention period has expired: " + exception.getMessage());
                }
                throw new RuntimeException(exception.getMessage());
            }

        }
    }

}
